1. Field of the Invention
The present invention relates to an optical interconnect, and specifically to maintaining a constant communication distance of optical interconnect in a backplane structure in which a plurality of blades can be inserted into a plurality of fixedly arranged slots.
2. Related Art
Even an optical communication function of a large-scale computer, which used to be divided into multiple kinds of units in the past, has become able to be contained in a single board at a high density, allowing the construction of a high-bandwidth communication apparatus through the installment of a plurality of such boards.
A single board has a shape like a thin blade and therefore can be simply referred to as a “blade”, and when such a single board contains the function of a server, it can be referred to as a “blade sever”.
FIGS. 1(a) and 1(b) show an example of the configuration of a high-bandwidth optical communication apparatus. In the configuration example of FIG. 1(a), six blade servers can be inserted 150. Furthermore, the configuration in FIG. 1 (a) consists of peripheral equipment 100, a DVD Rom 110, a backplane 120, USB Port 130, battery 140, and a blade chassis 160.
Since functions needed for optical communication between computers are modularized, it can be configured so that either only a specific blade entirely implements a specific function, or that a specific function is distributed over and implemented by a plurality of blades (6 blades at the maximum in this example 150).
In order to accommodate a plurality of blades as being inserted into a high-bandwidth optical communication apparatus, a structure called a “backplane,” such as 120, is prepared and contained in a blade chassis, such as 160. The blade chassis can also be called as a “base chassis”, “enclosure”, or “blade center,” etc.
FIG. 1(b) shows a manner in which a blade server is inserted into a high-bandwidth optical communication apparatus. FIG. 1(b) includes an example of a blade (server) 170.
FIGS. 2(a) and 2(b) show an example of the configuration of a backplane 120. FIG. 2(a) is a schematic view to illustrate an internal structure that is made up within a blade chassis. In addition to the backplane 120, the figure consists of slots 200, a ventilation hole 220, and a component 230.
A plurality of slots is fixedly arranged in the backplane 200 and 210. The fixed arrangement of the plurality of slots are not necessarily limited to a single row, but can be arranged over in two or more rows 200 and 210. A blade is selectively inserted into any of the plurality of slots through a connector prepared on the blade side.
In the above described structure, cables (optical fibers in the case of optical communication) for connecting each blade to other blades, and moreover cables for connecting each blade to peripheral equipment are integrated in the backplane to form an optical interconnect. Thus, simply inserting a blade allows the connection with other blades, to networks, and peripheral equipment 100. Such an integrated structure allows the wiring of the rear face of a high-bandwidth optical communication apparatus to be put together, thereby providing a flexible structure that allows easy replacement of a server at the time of extension or failure thereof.
Further, such a flexible structure allows the capacity for the optical communication apparatus to be expanded by increasing the number of the blades depending on the budget and scale, or allows for the capacity to be reduced by leaving a vacant slot from which a blade is drawn out as it is. Usually, the capacity is set according to a peak performance, and a minimum necessary number of blades are installed. This is also an advantageous structure for cutting down ineffective electric cost needed for keeping useless blades in standby, as well as in the viewpoint of hardware conservation, such as maintenance cost.
If there is a margin in the area of the backplane and the strength of the backplane itself can be secured, there can be a case that a ventilation hole 220 is provided to secure airflow from the front face through to the rear face. But indeed, as the larger the size of the hole to be provided, the more attention should be paid to the rigidity of the backplane 120 itself, especially when the thickness of the substrate thereof is small.
FIG. 2(b) is a circuit diagram showing the relationship in which blades 1 to 6 are connected to each module within the blade chassis. Some of the modules are provided as being inserted as blades, and some are implemented as components in the areas other than the locations of the slots prepared on the backplane, such as area 230.
FIG. 3 is a rear view of a high-bandwidth optical communication apparatus. While FIGS. 1(a) and 1(b) are views from the front side, this figure shows the opposite side.
FIG. 3 consists of a power module 300, a management module 310, a switch module bay 320, a blower 330, and a serial module bay 340.
As shown in FIG. 3, a power module 300 and a blower 330, which is a cooling fan, can be provided utilizing, not the side where the blades are inserted, but the rear face (the side where slots do not protrude) of the backplane, that is, the rear face side of the blade chassis. Thus, an apparatus which can be shared by blades 1 to 6 can be shared wherever possible. In addition, various bays are prepared as well.
Nevertheless, as long as blades are expected to be selectively inserted into any slots, such as when three of the plurality of blades is to be inserted into any slots, three different combinations of communication distance can take place. This is true even for the combination of optical interconnects between two of those blades.
If there is a difference between the communication distance (peer-to-peer communication distance) of a blade-to-blade, physical optical interconnect, between two blades, which are one combination among the blades being inserted, and the peer-to-peer communication distance between two blades, which are another combination among the blades being inserted, then the scheduling control becomes complicated depending on the communication scheme. In this viewpoint, there is still room for improvement in the management of the wiring of cables.
FIG. 4(a) shows the configuration of the optical cables in U.S. Pat. No. 6,678,439 B2, and FIG. 4 (b) shows (what seems to be) an explanatory diagram of the fiber optical cable of that patent. U.S. Pat. No. 6,678,439 B2 provides a “Wavelength Division Multiplexing and Broadcast Optical Interconnection Apparatus.”
As shown in FIG. 4(a), a WDM (wavelength division multiplexing) plate 1 is prepared for each of a WDM assembly 20 and a WDM assembly 30 by a communication scheme using WDM. Since the communication from a laser transmitter 11 and a detector diode receiver 12 comes together radially toward a fiber optic cable 13, it is (seems to be) set that the communication distances become substantially equal to each other.
Nevertheless, the structure in U.S. Pat. No. 6,678,439 B2, in which communication distances are equalized, merely results from a geometric property that any communication distance becomes equal in length as long as it lies along a plurality of diameters that radially extend from the center (there is a transmitter exit aperture 4 at the center) of a disc circle.
Moreover, the structure of the WDM plate 1 is merely a structure that three-dimensionally receives light from eight radial directions. It is not expected to receive a blade server, nor to arrange the slots radially (three-dimensionally) and fixedly. It can be for that reason that the WDM plate is not named as a backplate or backplane.
As stated above, FIG. 4(b) is an explanatory diagram of the simplified configuration of the fiber optic cable of U.S. Pat. No. 6,678,439 B2. In an attempt to make a simplified explanation, U.S. Pat. No. 6,678,439 B2 (seems to) describe the configuration of a bundle of fiber optic cable for a, seemingly, broadcast-star topology with constant latency that can be expressed by the following:Li+M+Ni=Const(i=0, 1, . . . , n),where, L=Const (i=0, 1, . . . , n), andwhere, N=Const (i=0, 1, . . . , n).
The fiber optic cable 13 seems to establish a link as a bundle between the WDM assembly 20 and the WDM assembly 30. Nevertheless, a plurality of fibers which are branched from the both ends of the bundle of the fiber optic cable forming the broadcast-star topology are merely configured to have a constant length from the branching point as with each other.
It is noted that the broadcast-star topology, which is a widely used topology at the present time, refers to a physical layout of network in which nodes are collectively connected to a central repeater.
Further, “A High-Speed Optical Multi-drop Bus for Computer Interconnections,” 16th IEEE Symposium on High Performance Interconnects, Applied Physics A: Material Science & Processing, Volume 95, Number 4, pp. 1067-1072, Michael Tan et al. shows a communication scheme based on an optical multi-drop bus, which can be applied to the configuration of the present invention. That is an example of scheduling control, showing that significant expansion of memory can be achieved by exploiting a plurality of modules connected to a bus through a backplane as a commonly-used technology referred to as optical multi-drop coupling.
As a general technical explanation, a broadcast-star topology made up of hubs and repeaters is logically similar to a bus, and attention needs to be paid to the occurrence of collisions.